1. Field of the Invention
The present invention relates to an improved process and apparatus, including improved gas nozzle devices, for the soldering and desoldering of electrical circuit components to a printed circuit board. More specifically, the present invention relates to improvements or modifications in gas nozzle devices to render them useful for the attachment or detachment of electrical circuit components having a land grid array of solder connections to a companion array of circuit connections printed onto the surface of the printed circuit board.
2. State of the Art
A variety of soldering/desoldering machines are known for the attachment and deattachment of electrical circuit components from areas of crowded printed circuit boards, adjacent to other closely-spaced soldered components which are not to be disturbed. Reference is made to commonly-assigned U.S. Pat. No. 5,044,072 for its disclosure of such an apparatus, including vacuum gas nozzles for holding an electrical component relative to a PCB surface and for directing hot gas through slots therein downwardly against peripheral component leads and corresponding peripheral solder pads on the PCB. The hot gas melts the solder to permit the attachment or deattachment, as desired, of the component relative to tile PCB surface.
While such known processes and nozzles produce excellent results with conventional peripheral-lead components, they are not satisfactory for use with face-down or land grid array (LGA) components, including ball grid array (BGA) components, solder grid array (SGA) components, and column grid array (CGA) components. Such components comprise a grid array of spaced solder connections distributed over the undersurface thereof, for electrical connection to a companion array of spaced circuit connections exposed at the upper surface of the printed circuit board. Conventional soldering/desoldering machines and conventional vacuum/gas nozzles are unreliable and ineffective for the soldering or desoldering of LGA components. Therefore such components must be soldered in an oven environment during production soldering of the entire PCB assembly. Reworking or individual component selective/desoldering of these hidden lead LGA components is substantially impossible since it requires the provision of a uniform heat pattern through the component to melt all of the solder balls or columns of the array uniformly and substantially simultaneously.
The use of LGA components is growing in view of the advances in technology and the complexity of electrical circuit components which require a greater number of electrical connections which the peripheral area of the component body is not able to accommodate. LGA technology permits a large number of terminal connections to be printed in the form of a grid or array on the undersurface of the component, which connections are hidden beneath the body of the component being attached or detached. The exclusion of peripheral or perimeter leads, extending outwardly from the component, enables components to be mounted in closer proximity to each other, which saves vital PCB surface space or area to enable an increase in component population or a decrease in PCB size.